Campylobacter jejuni (C. jejuni), a gram-negative microaerophilic bacterium, is a leading cause of bacterial diarrhea and enterocolitis in children and adults in both developing and developed countries (Walker R I et al, Microbiol. Rev. 50(1): 81-94, 1986; Kim N W et al, J. Bacteriol. 174(11):3494-3498, 1992; Chan V L and Bingham H L, Gene 101:51-58, 1991). Clinical symptoms of Campylobacter infections range from watery diarrhea to inflammatory dysentery and bloody diarrhea (Cover T L and Blaser N J, Ann. Rev. Ned. 40:269-285, 1989; Walker R I et al, supra). Complications from C. jejuni infections have included Guillain-Barre syndrome, a neurological disease which may lead to respiratory paralysis and death, toxic megacolon, acute mesenteric adenitis syndrome, and reactive arthritis (Kaldor J and Speed B R, British Medical J. 288:1867-1870, 1984; Johnson K et al, Acta. Med. Scand. 214:165-168, 1983; Walker R I et al, supra).
C. jejuni is commonly found in surface water, in animals such as cattle, sheep, goats, swine and poultry, in industrial wastes, and in many different types of foods including unpasteurized dairy products. Human pets such as dogs, cats and birds may also be infected with C. jejuni and may transmit the bacterium to humans. (Cover T L and Blaser M J, Ann. Rev. Med. 40:269-285, 1989; and Penner, J. L., Clin. Micro. Rev. 1:157-172, 1988).
Despite recognition of C. jejuni as a major human enteropathogen, an understanding of both the genetic organization and virulence mechanisms of this organism remains rudimentary. Campylobacteria have small genomes with a low-percent G+C and high A+T content. For instance, the C. jejuni TGH9011 chromosome is 1812 kb in size with a G+C content of approximately 30%. Within this A+T-rich genome, restriction enzyme sites high in G+C such as SacII (CCGGCC) and SmaI (CCCGGG) are infrequently found (Kim, 1992). On the basis of its size and G+C content, A C. jejuni chromosome should contain approximately 110 SalI (GTCGAC) recognition sites (McClelland, 1987). Surprisingly, all of the C. jejuni isolates analyzed to date contain only 5-6 SalI sites (Chang & Taylor 1990; Kim et al., 1992), and three of these sites are located within 23S rRNA encoding sequences (Kim et al.,1993; Kim et al., 1995). The three recognition sites for the enzyme SalI are each located within a conserved rRNA operon.